The invention relates to a method for producing nitric acid, in which ammonia is combusted on at least one catalyst mesh, in particular a platinum mesh, in the presence of oxygen, and the reaction gases are cooled.
The combustion of NH3 on a catalyst mesh is done at temperatures of 800-1000xc2x0 C., for instance, in accordance with the following equation:
4 NH3+5 O2xe2x86x924 NO+6 H2Oxe2x80x83xe2x80x83(1)
The NO produced in this reaction reacts, during and after the cooling down of the reaction gases to approximately 20-30xc2x0 C., with oxygen to form NO2:
NO+xc2xd O2xe2x86x92NO2xe2x80x83xe2x80x83(2)
In contact with water and oxygen, the desired nitric acid HNO3 is produced:
4 NO2+2 H2O+O2xe2x86x924 HNO3xe2x80x83xe2x80x83(3)
It has been found that as a secondary reaction in the catalytic NH3 combustion to form NO according to equation (1), undesired N2O (laughing gas) is also produced:
4 NH3+4 O2xe2x86x922 N2O+6H2Oxe2x80x83xe2x80x83(4)
which is not broken down in the ensuing stages in the production of the nitric acid.